This invention relates generally to apparatus and method for accurately transmitting condition data from an inaccessible device such as a rotating member to an accessible or stationary device such as a display or recording device. More particularly, this invention relates to an optical/electrical system for transmitting analog data from the rotating member and converting said analog data to digital data for use by the stationary device.
It is desirable for a variety of reasons to discern information regarding conditions of a rotating member such as a shaft or the like. This information includes torque as measured by a system of strain gauges, temperature as measured by a system of thermocouples, and other parameters as measured by an appropriate sensor or sensors.
The major problem in obtaining condition information from rotating or inaccessible members is transmitting the information accurately and reliably from the rotating environment to an accessible or stationary environment so that said transmitted data can be used. Prior to the present invention, apparatus for the purposes described has relied upon either AM or FM radio equipment, slip rings, or rotary transformers. These devices have proven to have excessive errors and have been heavy and bulky, and require significant electrical power. For apparatus which operates in hazardous environments such as in oil refineries and chemical plants, the electrical power required precludes the apparatus from meeting safety requirements. Additionally, when rotary transformers are used, the amount of data which can be effectively transmitted is often limited by cross-talk in the rotary transformer. Further, the prior art devices have been known to suffer from electrical/magnetic interference of one type or another, which further deteriorates their accuracy and reliability.
The present invention is an improvement over the prior art in that it uses fiber optic technology to transmit the data from the rotary member. The data transmission system includes an arrangement of infrared light emitting diodes (LEDs) on the rotating member and a system of stationary optical receivers mounted around the rotating member. During operation the data from the rotating member is accurately transmitted by actuating the rotating LEDs in a preselected digital sequence. The light signals so provided are received by the stationary receivers and transmitted through a fiber optic channel to utilization means including a computer or the like for operating a display device or a recording device, as the case may be.